I think you are being a trifle too pessimistic. OK; I tend to be optimistic about these things, but the Winchester stamp looks so crisp that I do not think there has been any wire-brushing, bead-blasting or whatever. In such case, the first to go would be the fine curves of the "Winchester" stamp and the small print of the trade mark" beneath it. And they both seem to be excellent. So maybe it is just fossilized grease.
And the fine state of the stamps leads me to think that the striations on the receiver/sight block are original ripple lines left by wartime "Cut out the beauty treatment" machining. Underneath the yellow, those components may be a lot more original than you feared, or hoped.
So, quite definitely, no kind of abrasive - otherwise YOU might be the one who spoilt the original surface. I would keep on with the acetone, but you can go faster with a brass or bronze wire brush* - use an old bore brush - which will also get the last of the yellow stuff out of the lettering.
More pics of the other parts, please - or have I overlooked something - I only see 3 photos?
*The brushes used for suede leather are ideal.